(Referring to a collection of information). That means these two examples can be correct: The grammatical rules have evolved from using the singular Latin noun datum to using data for a collection of information. It regards the noun as both singular and plural.Īccording to the Wall Street Journal, many standard dictionaries and books on language now accept data as singular and plural. The dictionary entry from the Merriam-Webster Dictionary states that data is a piece of factual information used as a basis for discussion, reasoning, or calculation. Between this data or these data, it’s these data. In the same way, when choosing between data was or were, the correct form is data were. Hopefully this helps clarify how selection.data and selection.datum() differ from each other both when providing data as an input argument and when querying for the bound datum by not providing any input arguments.Data are is the right way to use the noun in a sentence because it’s in plural form. ![]() The former returns the bound datum for the selection ( "a" in the example above) whereas the latter returns the bound datum within an array ( in the example above). Note that even if selection has a single element, selection.datum() and selection.data() return different values. So in the example above with the selection consisting of DOM elements with bound datum of "a", "b" and "c", selection.datum() would simply return "a". Selection.datum() only makes sense for a single selection as it is defined as returning the datum bound to the first element of the selection. It is important to note that if selection is a single element with (by way of example) the datum "a" bound to it, then selection.data() will return and not "a" as some may expect. So, if your selection includes 3 DOM elements with the data "a", "b" and "c" bound to each respectively, selection.data() returns. Selection.data() will take the bound datum for each element in the selection and combine them into an array that is returned. InĬontrast, selection.data() only binds the entirety of data Multiple DOM elements, then selection.datum(data) will bind theĮntirety of data to every single element in the selection. Warning: Many people believe that selection.datum(data) is equivalent to selection.data() but this is only true if So if you want to bind an entire array data = to every DOM element in your selection, then selection.datum(data) will achieve this. This simply assigns the entirety of data to all elements in the selection as a whole without splitting it up as in the case of data-joins. Selection.datum(data) bypasses the data-join process altogether. Each element of the selection will only have a single datum element of data bound to it. The end result of this is if you pass in an array data =, an attempt is made to join each individual data element (i.e. Selection.data(data) will attempt to perform a data-join between the elements of the data array with the selection resulting in the creation of enter(), exit() and update() selections that you can subsequently operate on. Moreover, both of these methods can also be invoked without any input arguments in order to query the bound data/datum in the selection, in which case they once again behave differently and return different things.Įdit – I posted a slightly more detailed answer to this question here, but the post below pretty much captures all the key points regarding the two methods and how they differ from each other. Even in that scenario, the two behave differently if the selection is a single element versus when it contains multiple elements. ![]() ![]() After having looked into this a bit, I’ve found that the answers here on SO are not complete as they only cover the case when you invoke selection.data and selection.datum with an input data parameter.
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